(a) Field of the Invention
The present invention relates to a board having connection terminals, and more particularly to a board having springy connection terminals which are fixed to pads provided on a substrate, and which are used to establish electrical connection to an object to be connected such as an IC package by being pressed to pads provided on the object to be connected (hereinafter, the board is referred to as a “board with connection terminals”).
(b) Description of the Related Art
For mounting an IC package or the like on a mounting board such as a printed wiring board, there are various methods of electrically connecting pads disposed on the package and pads disposed on the board.
Among the methods, there is a method called an LGA interconnection using an LGA (land grid array) socket. The LGA socket includes a plurality of elastically deformable and electrically conductive members (spring connection terminals) disposed between the package and the board. By interposing such spring connection terminals between the package and the board, an appropriate contact force is generated between pads of the package and pads of the board, and thus a stable electrical interconnection is secured.
As a technique related to such related art, there is a technique in which the mounting is performed by inserting one by one springy and electrically conductive terminals into an insulative housing of an LGA socket, as described in U.S. Pat. No. 7,264,486. In the mounting structure disclosed in U.S. Pat. No. 7,264,486, the spring connection terminals are fixed to through-holes formed in the housing, respectively, and each spring connection terminal includes a spring portion housed in the through-hole, and connecting portions continuous to upper and lower end portions of the spring portion, respectively. One of the connecting portions projects, together with a portion of the spring portion, from the top surface of the housing. The connecting portion provides the electrical connection between the connection terminal and the object to be connected by coming into contact with a surface of a pad, which is pressed on the connecting portion, of an object to be connected (for example, a wiring board).
Since the portion of the spring portion continuous to the connecting portion projects from the top surface of the housing, the projecting portion of the spring portion shifts (is displaced) mainly in a planar direction of the pad when the pad of the object to be connected is pressed on the connecting portion. This causes the connecting portion to shift (slip) on the surface of the pad at the time of being pressed by the pad.
As described above, in the case of the technique related to the related art board with connection terminals (U.S. Pat. No. 7,264,486), the projecting portion of the spring portion shifts in the plane direction of the pad when the pad of the object to be connected is pressed on the connecting portion. Hence, the connecting portion largely shifts (slips) on the surface of the pad. For this reason, the pad in the direction of the shift of the connecting portion needs to have a large width. This may lead to a disadvantage that the pads cannot be arranged at a narrow pitch.
The applicant of the present invention has proposed a technique to address the disadvantage (Japanese Patent Application No. 2009-128785 filed on May 28, 2009). The technique disclosed therein makes it possible to arrange the pads at a narrow pitch by forming each spring connection terminal into a specific shape.
In addition, the above-described related art (U.S. Pat. No. 7,264,486) is disadvantageous in terms of efficiency of mounting, because the mounting is performed by inserting the spring connection terminals one by one into the housing. In particular, under a situation where the demands for down-sizing and high density mounting have brought about arrangement of the terminals at an increasingly narrower pitch and an increase in the number of pins used, even the arrangement by the one-by-one insertion is difficult to perform, and the time and labor for the arrangement is increased with the increase in the number of the terminals. Accordingly, the above-described related art (U.S. Pat. No. 7,264,486) is further disadvantageous under such a situation.
As a countermeasure against this, a method is conceivable, for example, in which, for mounting a plurality of connection terminals on a housing, the plurality of connection terminals are aligned on a jig so as to meet the intended arrangement of terminals, the terminals are mounted by being transferred from the jig to the housing. In this method, it is necessary for the jig for the alignment to be provided with recessed portions for fixedly holding portions of terminals (end portions on the side opposite to the side of mounting on a board) so as to meet the intended arrangement of the terminals. The spring connection terminals are casted in the recessed portions, respectively.
The applicant of the present invention has proposed a technique embodying this method (Japanese Patent Application No. 2009-150587 filed on Jun. 25, 2009). The technique disclosed therein facilitates the casting of spring connection terminals to a jig by shaping each spring connection terminal into a specific shape. This method requires a jig for aligning the spring connection terminals. Here, it is desirable also from the viewpoint of simplifying the process if the connection terminals can be directly mounted on the board without the use of the jig. However, under the current situation where terminals are arranged at an increasingly narrower pitch and an increasingly larger number of pins are used, it is technically difficult to directly mount the connection terminals on the board. On the other hand, with the down-sizing being demanded, it becomes necessary to make the board itself as thin as possible. Here, since the thinning causes problems of warp, distortion, and the like, a certain countermeasure is required against the warp and the like, even if the connection terminals are directly mounted on the board.